Tread stock



May 28, 1929.

w. B. wEsco'rT 1,714,995

TREAD STOCK y Filed 0012. .28, 1925 2 Sheets-Sheet l gnou/loi v/l//zz/AW? 41561275 .aff/577%! TREAD STOCK Filed oct. 28, 1925 2sheets-sheet 2 Y me/nto@ retenue `May 2s, 1.929.

UNITED STA-Tas WILLIAM BURTON WESCOTT, O F DDVER,

MASSACHUSETTS, ASSIGNR T RUBB-ER LATEX 'RESEARCH CORPORATION, OF BOSTON,MASSACHUSETTS, A CORPORATION 0r MASSACHUSETTS.

TREAT) STOCK.

Application mea october as, 1925. serial No. 65,439.

. This invention relates to treadstock; and it' being,initially,.that^of the4 rubber but be ing sharply'arrested at a givenpoint while the exibility of the article is that of the rubberl butslightly limited beyond a certainl point; all as Amore fully hereinafterset forth and as claimed. y An ideal shoe sole is resilient and isflexible in a longitudinal direction butresists spreading or' extensiontransversely and for some purposes is advantageously less exibletransversely than longitudinally, conforming to the natural movements ofthe foot as Well as preventing deformation of the shoe; shouldfurthermore be Waterproof be permanently nonfslipping and be adapted tothe usual shoe making processes, Ii. e. easily skived, channeled andstitched, rmly retaining the stitch, and be of a strong durable nature.None of the materials now. in use meets all. of these requirements infull measure. Leather is not resilient and if dense enough to preventdeformation of the shoe .is relatively inflexible and furthermore itcannot, as a shoe sole, be made permanently Waterproof. The currentlyused rubber soles and --the l recently introdued crude rubber plantationcrepe soles While resilient and Waterproof do not hold stitches, spreadbadly and are rather more slippery when wet than is leather.. l

It is the obj ect of the present invention to provide a material meetingmore nearly the stated requirements. To this end I make a .duced bycoagulation of latex as by aceticacid 100 sheeted.material composedmainly of rubber or rubber compound but containingn dis-y tributed beror thread in lessl amount; this distributed ber being vso containedvasto give a reinforcing action in all directions and to appear, in part,at the wearing surface, thus increasing the surface coefficient `offriction.

and producing'a substantially non-slip surface' these characteristicspersisting as the I sole 1s worn down through the body of rubber andber. v Ihe ber ofthe sole is, in part,

tailed. With less than 50 per cent rubber the obtained with phenol'condensation products,

and in a transverse direction at least, put` under tension by anydeformation, thus limit-- ing .the extensibility but is so varrangedthatthe longitudinal exibility at least is substantially that of therubber compound up to a certain point. I nd by experience that it isnecessary for a composite article, containing -both rubber and berdistributed therethrough of such substantial length as to givereinforcement and limit 'extensibilit to carry more than 50 per centrubber or ruis),- ber compound'in order that it may evince the usualrubber properties sufficiently for usevas tread stock. Using long berand less amounts of rubber the material amounts to cemented ber rather,than reinforced rubber. If the natural vinterstitial Avoids o fcompacted ber be just lled with rubber the slightest. exing or extensionputs the bers under tension and the reaction of the cementedl ber masshas substantially none of the usual rubber properties. If on the otherhandthe bers are isolated and spaced apart by a relatively large amountof rubber, then the rst reaction to an applied force, is-substantiallythat normal to rubber, but as the reinforced rubber is compressed, exedand extended thebers'come into play and the usual rubber characteristicsare more or less greatly churcemented bers form a stiff hard mass,vcomparable to 'that obtainable with any slightly flexible bond suchl aspolymerized China Wood (tung) Oil or even the harder bonds such as suchas bakelite and the like. It is merely cei. mentedber. From 50per centof rubber upward the physical characteristics change very rapidly.Actually about 65 per cent rubber is a practical Working minimum. Fortread purposes the rubber is best but; slightly vulcanized and is oftenadvantageously used raw, that is uncured.

vRaw rubber-existsm'two forms: onel pro-l or other convenient chemicalcoagula'nt,and the other^gelled rubber obtained by simply drying thelatex. Either may be here used, or latex itself lmay be directlyemployed.

Rubber may be used with or Without the adm mate and uniformdistributionrof ber l through rubber by the direct. use of lateiz itselfas a source of rubber. For the present pur oses, latex may be defined asthe milky juic of Hevea. It ordinarily carries around per cent ofrubber, together with various other solid bodies, resins, proteids,enzymes, etc. As stated, the presence of more than 50 per cent of rubberin the material is required to give it the ordinary .rubber properties.Fibers and fabrics will hold by simple capillarity from 100 per cent to200 per cent of latex, giving with a 30 per cent latex and on a drybasis a final material carrying 23 per' cent tol 37 per cent of'rubber;4 or an amount materially less than is deemed necessary for thepresent purposes.

More latex, however, and sufficient for the present purposes, canbe'incorporated with fiber by various methods, for example, by pro--ducing an open-textured material capable of holding liquid latex in voidspaces as well as in capillary spaces, and adding latex in such a Way asto avoid collaps A specially prepared open-textured sheetor bat may besimply placed in a shallow 'pan and the pan filled with the right amountof latex; this v latex being then either gelled on the fiber byevaporation or coagulated by addition of alittle acid. This gives a ofrubberFof less dimensions and containing distributed fiber inanyproportions desired.

This method, or'that hereinafter described, produces a porous sheet ofrubber and fiber, which should be carefully dried at a low temperature,best with the use of a'high vacuum, to a point where the watencontainedis less than thatnormal to the contained fiber under atmosphericconditions. The drier the fiber can be made the better. On nowcompressing, as byrolling, the open teX7 tured sheet, the rubbersurfaces weld together and a-comp'act sheet is obtained.

The heavy pressure of .the compressing rolls tends to put most of thefibers, both laterally and longitudinally, in a position t0 come bytension under an applied force, and there 'results a mass having' a verylimited fiexibility and substantially no extensibility,

f but as...v the amount of.y rubbery` is ordinarily kept at about percent the article has,

though slightly diminished, the .characters4 istie resiliency of rubber.

In-the present'invention it is desired to give limited longitudinaliexibility without however diminishing. the desirable lateralnonextensibility, and the final rolling is per-A formed between rolls ofdifferent peripheral speeds. In so doing the material banks up more orlessI resulting in a peculiar transverse l structure from aforeshortening' and corre.

sponding thickening ofthe sheet; which is in effect a sort of pleatlng.Supercially the article appears as' if transversely corrugated;

, but the lcorrugation's represent a eculiar structure extending throughthe s eet by(L fiat body or sheet rolled upor crumpled a little. Withoutin terfering with the transverse inextensibility, a freer longitudinalfiexibility and extensibility are given. vOn longitudinal extension thesheet yieldsA at first as freely as rubber sheet without reinforcement,but as the fibers come under tension there is an abrupt limit to theextension. Laterally this yielding does not occur.

Because of the' presence of the included, fiber, most of which is inuniform distribution throughout the body of the material the sheet isreadily stitched and the stitchesV are firmly held by the surroundinfibers under tension. The included fiber a so produces a high surfacecoefficient of friction and where the. fiber is in substantially uniformdistribution a shoe sole or tread never wears smooth enough to becomeslippery. In cutting or punching shoe sole shapes from a sheet of thismaterial the -long axis of the sole is so, laid as to yield a soleflexible lengthwise but not extensible crosswise.

Tread stck made under the present invention with the aid of latex as aninitial material may be, and` advantageously is, unvulcanized oruncured.This is for the reason that raw rubber, either coagulation rubber orgelled rubber, has physical properties advantageous in. a shoe-isole.However, in using latex, if cured final products are desired they may besecured by the simple 'expedient of incorporating flowers of sulfur inthe fibers prior to impregnation; or by simply adding sulfur to thefluid latex and maintaining the suspensiorrby stirring, the rest of theprocess being as previously I described. After thefinalformationl of asheet of treadstock it may be cured in the Ordinar;7 ways; either beforeor after cutting.

In the accompanying illustration I have shown more or lessdiagrammatically various matters susceptible of illustration inconnectionwith the present invention. Invthis` showing,

Figure 1 is a view of. a complete sole having the structure hereinbeforecalled creped and made by the preferred mode ytaining fiber goingbetween rolls giving a chatter.` X

Referring first to Figure 3, felt or batted fiber which may be stitchedor knitted to some extent in order to maintain its lofty structure isfed from roll 1 through a bath of latex in tank 2, various pairs ofrolls, 3, 4.and 5 being provided to assist in impregnation. Idler rolls6 guide the sheet in a circuitous path through the bath. Dam 7 is justbelow the upper liquid level of the latex. Beyond it is another idler 8and a chute 9 extending downward to a lower level. Latex overfiows .intothis chute and` is there under some hy- '15 drostatic head. Passingdownward through the chute the bat is exposed to an acid'spray fromspray means 10 which skin coats`it, forming a sealing film. The excessacid outside the sheet flows downward and prevents adhesion of therubber to the metal members of the chute.' Beyond the lower level of thechute the traveling sheet enters acid bath 11. In this 'bath the skincoated bat 12 tends to oat but is carried forward by rollers 13 25Vwhich cause it to pass through well 14 of the acid bath as -festoons Itsperiod of travel through the well is sufficient to produce completeinternal coagulation of the contained i latex. The sheet which is nowinteriorly a spongy textured or honeycombbke structure of fiber, rubber,and included watery liquid, passes upward out of the acid bath betweensqueezing rolls l'which rupture the outer coating and express thecontained watery \liq'uid.c Upon re-expansion beyond these-I squeezerolls, the sheet takes'up water vfrom spray members 16. The sheet isthen compressed by rolls 17, re-wet by sprays 18, recompressed by rolls19 sprayed from 20, and

4o so on; squeezing and wetting being repeated as many times as to bedeemed necessary for washing.

AA/fter leaving-the'lastpair'of lsqueeze rolls, the moist sheet isldried in any convenient manner at a vlow temperature to get rid ofwater. Iv find .it best" to dry under vacuum at a temperature notexceeding 17 0 F. After drying, the warm spongy mass is compressed inany suitable way, asl by a platen press or by rolls, causing the driedraw rubber sury faces to weld together. In Fig. 4 I have I shown theeffectof producing'this welding between rolls 2l and 22 having acertain' l amount of chatter.- As will be noted, the mal terial banks upperiodically more or vless as -indicated at A23, this' causing theinternal structure shown in Fig. 2as wellas the creped surface'. 0 p Inthe structure of Flgure 3, 1t is of ad- 6ol vantage to providevmeans'for varying the width of chute 9 at its lower end to accom,

modate material of` different thicknesses. While it is not essential itis desirable that immediately upon the formation of the surface skincoating or film the material shall be subjected to sufficient rubbing topack the reticulate structure of the film.- For this reason I ordinarilymake the lower end of the chute. variable. This may be conveniently doneby making the portion below the acid sprays 10 of adjustable plates ofmetal 24V and 25. Aluminum plates 3 or 4 inches long are suitable. Theunder part 24 may be, as shown, fixed and the-upper part 25 hinged toallow it to be swung or moved. Hinging means are shown at 27. y

In the accompanying claims where I speak of rubber I mean to includerubber or rubber i material from any sources. The rubber may be whollynew rubber, as in using plantation -sheet or latex or it may be in partreclaimed rubberv from any source. Rubber surrogates such as boiled oil,gilsonjte etc. may form part of the material used. Likewise, the rubbermay contain various fillers, and woven fabrics'may be included in thefinished product, and the exterior corrugated appearance of the sheetmay be retained or removed.

What I claim is y 1. As a newl tread, stock, sheeted material composedof rubber with a minor amount of relatively long fiber distributedtherethrough y.

in such manner asto reinforce said rubber in all directions, saidsheetedmaterial being pleated as a whole to haye more extensibility in onedirection thanin another.

2. As a new tread stock, sheeted material consisting mainlv of rubbercontaining a mino-r amount o'f distributed fiber, such fiber being insuch arrangement :is to limit extensibihty in one direction whilepermitting .maximum flexure in another direction at right anglesthereto, the fiber being speeif.

ically crumpled in the direction of fi'exibility.

3. A tread stock consisting of' rubber containing distributed fibe'r inrandom arrange- YIMmentand in amount less than the amount of rubber,said sheet being pleated in one direcin random arrangement andbeingspecially crumpled in one direction of a sheet and not crumpled in adirection transverse thereto,

said ber being less than 50 per cent of the whole mass. i

fixed my signature. r

WILLIAM BURTON WES'COTT.

In testimony whereof, I havevhereunto'af-

